Solid-state radiation transducer devices having at least partially transparent buried-contact elements, and associated systems and methods

ABSTRACT

Solid-state radiation transducer (SSRT) devices having buried contacts that are at least partially transparent and associated systems and methods are disclosed herein. An SSRT device configured in accordance with a particular embodiment can include a radiation transducer including a first semiconductor material, a second semiconductor material, and an active region between the first semiconductor material and the second semiconductor material. The SSRT device can further include first and second contacts electrically coupled to the first and second semiconductor materials, respectively. The second contact can include a plurality of buried-contact elements electrically coupled to the second semiconductor material. Individual buried-contact elements can have a transparent portion directly adjacent to the second semiconductor material. The second contact can further include a base portion extending between the buried-contact elements, such as a base portion that is least partially planar and reflective.

TECHNICAL FIELD

The present technology is related to solid-state radiation transducerdevices and methods of making solid-state radiation transducer devices.In particular, the present technology relates to solid-state radiationtransducer devices having buried-contact elements that are at leastpartially transparent, and associated systems and methods.

BACKGROUND

Solid-state radiation transducers (SSRTs), e.g., light-emitting diodes(LEDs), organic light-emitting diodes, and polymer light-emittingdiodes, are used in numerous modern devices for backlighting, generalillumination, and other purposes. FIG. 1 is a partially-schematic,cross-sectional view of a conventional LED device 100 having a lateralconfiguration. As shown in FIG. 1, the LED device 100 can include agrowth substrate 102 under an LED structure 104 with an active region106 positioned between an N-type layer 108 and a P-type layer 110. Thedevice 100 can also include a first contact 112 electrically connectedto the P-type layer 110 and a second contact 114 electrically connectedto the N-type layer 108. As shown in FIG. 1, the second contact 114extends across only a small portion of the N-type layer 108. This typeof limited connection between the second contact 114 and the N-typelayer 108 can cause poor current spreading within the N-type layer 108,especially when the N-type layer 108 includes N-type gallium nitride,which has relatively low lateral conductivity. Poor current spreadingcan cause portions of the device 100 to be underutilized and can lowerthe lumen output and/or the efficiency of the device 100.

FIG. 2 is a partially-schematic, cross-sectional view of anotherconventional LED device 200 having a vertical configuration that canhave enhanced current spreading relative to the device 100 of FIG. 1.The device 200 includes a carrier substrate 202 and an LED structure 204with an active region 206 positioned between an N-type layer 208 and aP-type layer 210. During formation of the LED device 200, the N-typelayer 208, the active region 206, and the P-type layer 210 can be formedsequentially on a growth substrate (not shown) similar to the growthsubstrate 102 shown in FIG. 1. A first contact 212 can be formed on theP-type layer 210, and the carrier substrate 202 can be attached to thefirst contact 212. The growth substrate can then be removed and a secondcontact 214 can be formed, e.g., in a pattern, on the N-type layer 208.The device 200 can then be inverted to produce the orientation shown inFIG. 2. As shown in FIG. 2, the second contact 214 extends across asignificant portion of the N-type layer 208. This can facilitate currentspreading within the N-type layer 208 resulting in improved lumen outputand/or efficiency of the device 200. In the vertical configuration shownin FIG. 2, however, the second contact 212 can disadvantageouslyinterfere with emissions from the LED structure 204. The footprint ofthe second contact 212 can be reduced, e.g., to a series of lines asshown in FIG. 2, but cannot be made insignificant in this configurationwithout sacrificing the enhanced current spreading.

FIG. 3 is a partially-schematic cross-sectional view of anotherconventional LED device 300 having a buried-contact configuration inwhich the second contact can facilitate enhanced current spreadingrelative to the device 100 of FIG. 1 while interfering less with deviceemissions than in the device 200 of FIG. 2. Similar to the device 200 ofFIG. 2, the device 300 can include a carrier substrate 302 and an LEDstructure 304 having an active region 306 positioned between an N-typelayer 308 and a P-type layer 310. Also similar to the device 200 of FIG.2, the device 300 can include a first contact below the P-type layer310. As shown in FIG. 3, the device 300 can include a second contact 314with buried-contact elements 315 that extend through the first contact312, the P-type layer 310, and the active region 306, and partially intothe N-type layer 308. A dielectric layer 316 can electrically isolatethe second contact 314 from the first contact 312, the P-type layer 310,and the active region 306. The second contact 314 can be electricallyconnected to the N-type layer 308 at multiple transition regions 318distributed across the area of the N-type layer 308. Distributing thetransition regions 318 can enhance current spreading within the N-typelayer 308. Furthermore, since much of the second contact 314 is belowthe P-type layer 310, the second contact 314 can interfere less withemissions from the LED structure 304 than the second contact 212interferes with emissions from the LED structure 204 of the LED device200 shown in FIG. 2.

Although the buried-contact configuration shown in FIG. 3 is animprovement in many ways relative to the lateral configuration shown inFIG. 1 and the vertical configuration shown in FIG. 2, it still hassignificant drawbacks. For example, many modern LED devices includecolor-converting materials, e.g., phosphors, positioned in the path ofemissions from an LED structure. Color-converting materials can absorblight that an LED structure emits at a certain wavelength range and emitlight at a different wavelength range. Color-converting materialstypically release light in all directions, including back toward the LEDstructure. Reflection of the light emitted back toward the LED structurecan be an important factor in determining lumen output and efficiency ofa device. The uniformity of this reflection also can be important,particularly in display and projection applications. Conventional buriedcontacts typically interfere with this reflection and/or otherperformance-related reflection to some degree. For example, thetransition regions 318 shown in FIG. 3 can absorb light and causeundesirable dark spots in the near field. For this reason and/or otherreasons, there is a continuing need for innovation with regard to SSRTdevices, such as to improve the lumen output, efficiency, and outputuniformity of buried-contact SSRT devices.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present disclosure can be better understood withreference to the following drawings. The components in the drawings arenot necessarily to scale. Instead, emphasis is placed on illustratingclearly the principles of the present disclosure.

FIG. 1 is a partially-schematic, cross-sectional diagram illustrating anLED device having a lateral configuration in accordance with the priorart.

FIG. 2 is a partially-schematic, cross-sectional diagram illustrating anLED device having a vertical configuration in accordance with the priorart.

FIG. 3 is a partially-schematic, cross-sectional diagram illustrating anLED device having a buried-contact configuration in accordance with theprior art.

FIG. 4 is a partially-schematic, cross-sectional diagram illustrating anSSRT device configured in accordance with an embodiment of the presenttechnology and having buried contacts with transparent portions intapered vias.

FIG. 5 is a partially-schematic, cross-sectional diagram illustratingthe SSRT device shown in FIG. 4 further including a color-convertingcomponent and an encapsulant lens.

FIGS. 6A-6F are partially-schematic, cross-sectional diagramsillustrating selected stages in a method for making the SSRT deviceshown in FIG. 4.

FIG. 7 is a partially-schematic, cross-sectional diagram illustrating anSSRT device configured in accordance with an embodiment of the presenttechnology and having buried contacts with transparent portions instraight vias.

FIG. 8 is a partially-schematic, cross-sectional diagram illustrating anSSRT device configured in accordance with an embodiment of the presenttechnology and having a conformal transparent layer.

FIGS. 9A-9B are partially-schematic, cross-sectional diagramsillustrating selected stages in a method for making the SSRT deviceshown in FIG. 8.

FIG. 10 is a partially-schematic, cross-sectional diagram illustratingan SSRT device configured in accordance with an embodiment of thepresent technology and having buried contacts with conformal transparentportions in tapered vias.

FIG. 11 is a block diagram illustrating a system that incorporates anSSRT device in accordance with an embodiment of the present technology.

DETAILED DESCRIPTION

Specific details of several embodiments of solid-state radiationtransducer (“SSRT”) devices and associated systems and methods aredescribed below. The term “SSRT” generally refers to solid-state devicesthat include a semiconductor material as the active medium to convertelectrical energy into electromagnetic radiation in the visible,ultraviolet, infrared, and/or other spectra. For example, SSRTs includesolid-state light emitters, e.g., LEDs, laser diodes, etc., and/or othersources of emission other than electrical filaments, plasmas, or gases.SSRTs can alternately include solid-state devices that convertelectromagnetic radiation into electricity. Additionally, depending uponthe context in which it is used, the term “substrate” can refer to awafer-level substrate or to a singulated, die-level substrate. A personhaving ordinary skill in the relevant art will recognize that each stageof the processes described below can be performed at the wafer level orat the die level. A person having ordinary skill in the relevant artwill also understand that the present technology may have additionalembodiments, and that the present technology may be practiced withoutseveral of the details of the embodiments described below with referenceto FIGS. 4-11.

For ease of reference, throughout this disclosure identical referencenumbers are used to identify similar or analogous components orfeatures, but the use of the same reference number does not imply thatthe parts should be construed to be identical. Indeed, in many examplesdescribed herein, the identically-numbered parts are distinct instructure and/or function. Furthermore, the same shading is sometimesused to indicate materials in cross section that can be compositionallysimilar, but the use of the same shading does not imply that thematerials should be construed to be identical.

FIG. 4 is a partially-schematic, cross-sectional diagram illustrating anSSRT device 400 configured in accordance with an embodiment of thepresent technology. The SSRT device 400 can include a transducerstructure 402, a first contact 404, a dielectric 406, and a secondcontact 408 supported by a carrier substrate 410. As shown in FIG. 4,the SSRT device 400 can have a first side 412 and a second side 414facing away from the first side 412. The transducer structure 402 caninclude an active region 416 having a first side 418 and a second side420 opposite the first side 418. The transducer structure 402 canfurther include a first semiconductor material 422 at the second side420 of the active region 416, and a second semiconductor material 424 atthe first side 418 of the active region 416. The first contact 404 canbe electrically coupled to the first semiconductor material 422. Thesecond contact 408 can include buried-contact elements 426 and agenerally planar base portion 428 extending between the buried-contactelements 426. The buried-contact elements 426 can extend between thebase portion 428 and the second semiconductor material 424 and can beelectrically coupled to the second semiconductor material 424. Theburied-contact elements 426 can be at least partially transparent. Forexample, a portion of the buried-contact elements 426, e.g., a portionadjacent to the second semiconductor material 424, can have a primarycomposition that is conductive and transparent. This portion can berelatively small, e.g., less than about 10% by volume of theburied-contact elements 426, or relatively large, e.g., at least about50% by volume of the buried-contact elements 426. In some embodiments,the buried-contact elements 426 are entirely transparent. Suitableconductive and transparent materials for use in the buried-contactelements 426 and other conductive and transparent elements describedherein include, for example, indium tin oxide, doped zinc oxide (e.g.,aluminum-doped, gallium-doped, and indium-doped zinc oxide), conductivepolymers (e.g., polyaniline and poly(3,4-ethylenedioxythiophene)),carbon allotropes (e.g., carbon nanotubes and graphene), andcombinations thereof. In some embodiments, the buried-contact elements426 include indium tin oxide, zinc oxide, or a combination thereof

As used herein, elements positioned on or at the first side 412 of theSSRT device 400 can be positioned in the region bounded by the firstside 418 of the active region 416 and the external surface. Elementspositioned on or at the second side 414 of the SSRT device 400 can bepositioned in the region bounded by the second side 420 of the activeregion 416 and the opposing external surface. As materials are added toor removed from the SSRT device 400 during different stages of theformation process, the exterior surfaces of the first and second sides412, 414 of the SSRT device 400 may change. Accordingly, the externalboundaries of the first and second sides 412, 414 may change. Incontrast, the internal boundaries of the first and second sides 412, 414do not change, i.e., the first side 412 of the SSRT device 400 isconsistently bounded internally by the first side 418 of the activeregion 416, and the second side 414 of the SSRT device 400 isconsistently bounded internally by the second side 420 of the activeregion 416.

In conventional buried-contact SSRT devices e.g., the LED device 300shown in FIG. 3, regions between buried-contact elements andsemiconductor materials, e.g., the transition regions 318 shown in FIG.3, typically have relatively low reflectivity. This can result, forexample, from steps conventionally used to form an adequate electricalconnection between buried-contact elements and semiconductor materials.For example, in conventional buried-contact SSRT devices, metaltypically is deposited into buried-contact vias and then heated in anannealing step to form an alloy at interfaces between the metal and asemiconductor material. Without some form of annealing, an adequateelectrical connection to certain semiconductor materials, e.g., N-typegallium nitride, can be difficult to achieve. The alloy resulting froman annealing step typically has low reflectivity even if the contactbeing electrically connected to the semiconductor material includes ahigh-reflectivity material. Due to this and/or other factors,conventional buried-contact elements typically interfere with an SSRTdevice's ability to reflect light, e.g., backscatter radiation fromcolor-converting particles. As discussed above, such interference can bedetrimental to a variety of performance characteristics, e.g., lumenoutput, efficiency, and output uniformity.

With reference again to FIG. 4, in some embodiments configured inaccordance with the present technology, a transparent portion, member,or material can facilitate electrical connection between the secondcontact 408 and the second semiconductor material 424 without the needto form a low-reflectivity alloy. For example, in some of theseembodiments, light directed toward the transducer structure 402 cantravel through an electrical interface between the second contact 408and the second semiconductor material 424 to a reflective portion of thesecond contact 408 or to another reflective element proximate theburied-contact elements 426. A significant percentage of this light canbe reflected toward the first side 412 of the SSRT device 400, e.g., toimprove lumen output, efficiency, and/or output uniformity. In additionto or instead of this benefit, embodiments of the present technology canderive one or more other benefits from a transparent portion, member, ormaterial. For example, in a conventional buried-contact SSRT device,e.g., the LED device 300 shown in FIG. 3, some emissions from an activeregion typically are directed toward side surfaces of the buried-contactelements. For example, in the LED device 300 shown in FIG. 3, emissionsfrom the active region 306 can be directed through the dielectric layer316 to side surfaces of the buried-contact elements 315. Thereflectivity of these side surfaces can be disrupted as a secondaryconsequence of the annealing step described above. Furthermore, even ifthe side surfaces have high reflectivity, they can redirect emissions ina manner that disrupts output uniformity and/or decreases efficiency.With reference again to FIG. 4, in the SSRT device 400, some emissionsfrom the active region 416 may be transmitted through the buried-contactelements 426 with little or no interference. As a result, a performancecharacteristic of the SSRT device 400, e.g., lumen output, efficiency,and/or output uniformity, can be improved.

FIG. 5 is a partially-schematic, cross-sectional diagram illustrating anSSRT device 500 including the SSRT device 400 shown in FIG. 4, acolor-converting component 502, and an encapsulant lens 504. Thecolor-converting component 502 includes color-converting particles 506distributed within a matrix 508. Suitable color-converting materialswithin the color-converting particles 506 can include, for example,quantum dots and/or phosphor materials that exhibit luminescence.Examples of suitable phosphor materials include, for example,cerium(III)-doped yttrium aluminum garnet (YAG), neodymium-doped YAG,neodymium-chromium double-doped YAG, erbium-doped YAG, ytterbium-dopedYAG, neodymium-cerium double-doped YAG, holmium-chromium-thuliumtriple-doped YAG, thulium-doped YAG, chromium(IV)-doped YAG,dysprosium-doped YAG, samarium-doped YAG, terbium-doped YAG, andcombinations thereof, among others. The matrix 508 and the encapsulantlens 504 can be transparent and can have the same or differentcompositions. For example, the matrix 508 and/or the encapsulant lens504 can include a transparent epoxy, silicone, polyimide, acrylic, acombination thereof, or another suitable material. As discussed above,the color-converting particles 506 can absorb light that the transducerstructure 402 emits at a certain wavelength range and emit light at adifferent wavelength range. Some of the light that the color-convertingparticles 506 emit can be directed back toward the transducer structure402 as backscatter radiation. Other portions of the SSRT device 500and/or structures around the SSRT device 500 also can generatebackscatter radiation. For example, the encapsulant lens 504 can emit arelatively small amount of backscatter radiation. The SSRT device 500also may be incorporated into a reflective cavity (not shown) that helpsimpart directionality to emissions from the SSRT device 500, but alsoincreases backscatter radiation. The SSRT device 500 can have arelatively high reflectivity with regard to backscatter radiation fromthe color-converting particles 506 or another source. For example, theSSRT device 500 can have an average reflectivity of backscatterradiation from the color-converting particles at the buried-contactelements 426 greater than about 75%, e.g., greater than about 80%.

FIGS. 6A-6F illustrate a method for making the SSRT device 400 shown inFIG. 4 according to an embodiment of the present technology. Onlyselected stages are shown to illustrate certain aspects of the presenttechnology. At the stage shown in FIG. 6A, the transducer structure 402,including the active region 416 and the first and second semiconductormaterials 422, 424, has already been formed on a growth substrate 600.The SSRT device 400 is upside down relative to its orientation in FIG.4. The first and second semiconductor materials 422, 424 can be dopedsemiconductor materials. For example, the first semiconductor material422 can be a P-type semiconductor material, e.g., P-type galliumnitride, and the second semiconductor material 424 can be an N-typesemiconductor material, e.g., N-type gallium nitride. This configurationis suitable when the transducer structure 402 is formed on an opaque ortranslucent growth substrate 600 and subsequently attached to a carriersubstrate, e.g., the carrier substrate 410 shown in FIG. 4. In otherembodiments, the first and second semiconductor materials 422, 424 canbe reversed. The active region 416 between the first and secondsemiconductor materials 422, 424 can include a single quantum well,multiple quantum wells, and/or a single-grain semiconductor material,e.g., indium gallium nitride. In other embodiments, the transducerstructure 402 can include other suitable semiconductor materials, suchas gallium arsenide, aluminum gallium arsenide, gallium arsenidephosphide, or a combination thereof, among others. The transducerstructure 402 can be formed by metal organic chemical vapor deposition,molecular beam epitaxy, liquid phase epitaxy, hydride vapor phaseepitaxy, combinations thereof, or other suitable formation processesknown in the semiconductor fabrication arts.

At the stage shown in FIG. 6A, the first contact 404 also has beenformed. The first contact 404 can extend over a large portion of theunderlying first semiconductor material 422. In other embodiments, thefirst contact 404 can be formed over a smaller portion of the firstsemiconductor material 422. The first contact 404 can include areflective contact material, e.g., titanium, nickel, silver, aluminum,gold, or a combination thereof, among others. As discussed in greaterdetail below, during a subsequent processing stage, the transducerstructure 402 can be inverted such that the first contact 404 canredirect emissions, e.g., light, back through the transducer structure402 toward the first side 412 of the SSRT device 400. In otherembodiments, the first contact 404 can be made from a non-reflectivematerial, and the SSRT device 400 can include separate reflectiveelements positioned at the second side 414 of the SSRT device 400. Thefirst contact 404 can be formed using chemical vapor deposition,physical vapor deposition, atomic layer deposition, spin coating,patterning, combinations thereof, or other suitable formation processesknown in the semiconductor fabrication arts.

As shown in FIG. 6A, vias 602 can extend through the first contact 404,the first semiconductor material 422, the active region 416, and part ofthe second semiconductor material 424. In the illustrated embodiment,the vias 602 are shown tapered with narrowing cross-sectional dimensionsfrom a plane defined by the first contact 404 to the secondsemiconductor material 424. In other embodiments, the vias 602 can havea different shape. Furthermore, although the vias 602 are shownextending into part of the second semiconductor material 424, in otherembodiments, the vias 602 can end at or near a border of the secondsemiconductor material 424. In some embodiments, the vias 602 are formedbefore the first contact 404 and the first contact 404 is formed in apattern around the vias 602, e.g., to extend the vias. A variety ofsuitable processes can be used to form the vias 602, e.g., wet, dry,isotropic, and anisotropic etching processes performed in conjunctionwith photolithography, among others.

FIG. 6B shows a stage in the process after the dielectric 406 is formedover the first contact 404 and within the vias 602. In otherembodiments, portions of the dielectric 406 within the vias 602 andoutside the vias 602 can be formed separately. The dielectric 406 canelectrically isolate the first contact 404 from the second contact 408(FIG. 4) and electrically isolate the buried-contact elements 426 (FIG.4) from the first contact 404, the first semiconductor material 422, andthe active region 416. Suitable dielectric materials for use in thedielectric 406 include, for example, silicon dioxide, silicon nitride,and combinations thereof, among others. In embodiments in which portionsof the dielectric 406 within the vias 602 and outside the vias 602 areformed separately, the separate portions can have differentcompositions. In some embodiments, the dielectric 406 or at least aportion of the dielectric 406 within the vias 602 is transparent. Thedielectric 406 can be formed using chemical vapor deposition, physicalvapor deposition, atomic layer deposition, spin coating, patterning,combinations thereof, or other suitable formation processes known in thesemiconductor fabrication arts.

As shown in FIG. 6C, the dielectric 406 can be patterned, e.g., etchedor otherwise selectively deposited, to form exposed portions 604 of thesecond semiconductor material 424 at lower ends of the vias 602. Inother embodiments, a portion of the second semiconductor material 424can be etched along with portions of the dielectric 406 at the lowerends of the vias 602. In still other embodiments, the dielectric 406 canbe otherwise selectively deposited to leave portions of the secondsemiconductor material 424 exposed. The exposed portions 604 are shownflat in FIG. 6C, but can alternatively be three-dimensional. Forexample, etching, e.g., etching that removes a portion of the secondsemiconductor material 424, or selective deposition can be used toexpose a three-dimensional portion of the second semiconductor material424. The exposed portions 604 also can be roughened either at the timeof formation or through subsequent processing. Increased dimensionalityand/or roughness can be useful, for example, to increase the contactarea between a transparent portion of the buried-contact elements 426(FIG. 4) and the second semiconductor material 424. In some embodiments,increased contact area can mitigate deficiencies, if any, in anelectrical connection between a subsequently disposed transparentmaterial and the second semiconductor material 424. The dielectric 406also can be etched or selectively deposited to leave portions of thefirst contact 404 exposed for eventual connection to leads (not shown)at the second side 414 of the SSRT device 400.

FIG. 6D shows a stage in the process after the buried-contact elements426 are formed within the vias 602 (FIG. 6C). The buried-contactelements 426 can include, for example, indium tin oxide, doped zincoxide (e.g., aluminum-doped, gallium-doped, and indium-doped zincoxide), a conductive polymer (e.g., polyaniline andpoly(3,4-ethylenedioxythiophene)), a carbon allotrope (e.g., carbonnanotubes and graphene), a combination thereof, or another suitablematerial. The buried-contact elements 426 can be formed using chemicalvapor deposition, physical vapor deposition, atomic layer deposition,spin coating, patterning, combinations thereof, or other suitableformation processes known in the semiconductor fabrication arts. Asshown in FIG. 6D, the buried-contact elements 426 initially includeprotruding upper portions 606. FIG. 6E shows a stage in the processafter the protruding upper portions 606 have been removed, e.g., usingchemical-mechanical planarization or another suitable planarizationprocess known in the semiconductor fabrication arts. In someembodiments, a planarization process can be used to remove a portion ofthe dielectric 406 along with the protruding upper portions 606.

FIG. 6F shows a stage in the process after the base portion 428 of thesecond contact 408 has been formed on the buried-contact elements 426and the dielectric 406. The base portion 428 can be formed, for example,using chemical vapor deposition, physical vapor deposition, atomic layerdeposition, spin coating, patterning, combinations thereof, or othersuitable formation processes known in the semiconductor fabricationarts. The base portion 428 can include a reflective contact material,e.g., titanium, nickel, silver, aluminum, gold, or a combinationthereof, among others. Since the base portion 428 can be spaced apartfrom the second semiconductor material 424, the composition of the baseportion 428 can be selected according to factors other than its abilityto form an adequate electrical connection with the second semiconductormaterial 424. For example, the base portion 428 can include silver,which has very high reflectivity, but tends to form a poor electricalconnection with at least some semiconductor materials, e.g., N-typegallium nitride. In some embodiments, the base portion 428 is patterned,e.g., etched or otherwise selectively deposited, to form a network ofinterconnects (not shown) between the buried-contact elements 426. Inthese and other embodiments, the base portion 428 can include reflectivematerial at least at the buried-contact elements 426. Similarly, thebase portion 428 can include reflective material at least at transparentportions of the buried-contact elements 426. This can be useful, forexample, to facilitate reflection of light passing through transparentmaterial of the buried-contact elements 426. In some embodiments,portions of the second contact 608 not at the buried-contact elements426 and/or not at transparent portions of the buried-contact elements426 are not reflective or are absent, e.g., are removed or never formed.

After the stage shown in FIG. 6F, the growth substrate 600 can beremoved and the carrier substrate 410 (FIG. 4) can be attached to formthe SSRT device 400 shown in FIG. 4. The carrier substrate 410 can beconfigured to facilitate heat dissipation from other portions of theSSRT device 400. In some embodiments, the carrier substrate 410 has acoefficient of thermal expansion generally similar to that of thetransducer structure 402, which can decrease the likelihood ofdelamination. The growth substrate 600 can be removed, for example,using grinding, etching, or another suitable removal process known inthe semiconductor fabrication arts. In some embodiments, the SSRT device400 is releasably attached to a temporary support prior to removing thegrowth substrate 600. A releasable connection can be made, for example,using WaferBOND™ HT-10.10 available from Brewer Science, Inc. (Rolla,Mo.). After or before the growth substrate 600 is removed, the SSRTdevice 400 can be singulated, e.g., a wafer including the SSRT device400 can be diced. First and second terminals (not shown) can be includedat the second side 414 of the SSRT device 400 to connect leads (notshown) to the first and second semiconductor materials 422, 424. In someembodiments, the SSRT device 400 can be integrated into a circuitwithout the need for wire bonds.

Vias, buried-contact elements, and dielectrics around buried-contactelements can have a variety of suitable shapes that may affectperformance and processing of SSRT devices configured in accordance withembodiments of the present technology. For example, the buried-contactelements 426 are shown in FIG. 4 generally tapered with narrowingcross-sectional dimensions from a plane defined by the first contact 404to the second semiconductor material 424. This generally-tapered shapecan facilitate certain processing steps, such as deposition of thedielectric 406 shown in FIG. 6B. Uniform deposition of material ontowalls of straight vias, for example, can be difficult to achieve usingstandard deposition techniques. Some embodiments, however, includegenerally straight buried-contact elements. For example, FIG. 7illustrates an SSRT device 700 with a second contact 702 includingburied-contact elements 704 that have generally straight sidewalls froma plane defined by the first contact 404 to the second semiconductormaterial 424. The SSRT device 700 can further include a dielectric 706with generally-straight portions 708 extending around the buried-contactelements 704. The buried-contact elements 704 can be transparent andextend further into the second semiconductor material 424 than thestraight portions 708 of the dielectric 706.

In comparison to the generally-tapered buried-contact elements 426 shownin FIG. 4, the generally-straight buried-contact elements 704 shown inFIG. 7 can occupy less space within the SSRT device 700. This can allowa greater percentage of the SSRT device 700 to be dedicated togenerating emissions, e.g., light, without sacrificing electricalconnectivity between the second contact 702 and the second semiconductormaterial 424 or current spreading within the second semiconductormaterial 424. Moreover, the three-dimensional shape of the interfacesbetween the buried-contact elements 702 and the second semiconductormaterial 424 can facilitate enhanced electrical connection between thesecond contact 702 and the second semiconductor material 424. A processfor forming the SSRT device 700 can include forming generally straightvias, e.g., using an anisotropic etching step, and partially orcompletely filling the vias with dielectric material. The process canalso include forming generally straight channels within the vias, e.g.,using another anisotropic etching step, after adding the dielectricmaterial. The channels can be narrower than the vias and extend deeperinto the second semiconductor material 424 than the vias. After formingthe channels, the process can include partially or completely fillingthe channels with transparent material. Additional processing can besimilar, for example, to that described above with reference to FIGS.6D-6F or to that described below with reference to FIG. 9B.

Some embodiments configured in accordance with the present technologyinclude buried-contact elements that are partially transparent andpartially reflective. Furthermore, rather than being incorporated intoplug-type forms, transparent material can be incorporated into layers,portions of layers, or other suitable forms. FIG. 8 is a partiallyschematic cross-sectional diagram illustrating an SSRT device 800configured in accordance with an embodiment of the present technologyand having a second contact 802 including a transparent layer 804 thatis generally continuous and conformal. The second contact 802 canfurther include a base portion 806 and buried-contact elements 808having transparent portions 810 and reflective portions 812, with thetransparent portions 810 being between the reflective portions 812 andthe second semiconductor material 424. The transparent portions 810 canbe portions of the transparent layer 804, and the reflective portions810 can be portions of the base portion 806 of the second contact 802.The side surfaces of the reflective portions 812 are shown angled inFIG. 8. This can cause a greater percentage of light that the sidesurfaces reflect to be directed toward the first side 412 of the SSRTdevice 800 than if the side surfaces were straight. Each time light isreflected within an SSRT device, some energy loss to absorption occurs.Directing reflected light to the first side 412 of the SSRT device 800can reduce the total internal reflection within the SSRT device 800 andincrease its lumen output and/or efficiency.

In some embodiments, the location of an interface between a transparentportion and a reflective portion of a buried-contact element can beselected to enhance one or more performance characteristics of an SSRTdevice. For example, the broken lines in FIG. 8 show alternativeinterface locations 814 for interfaces between the transparent portions810 and the reflective portions 812. If the active region 416 isconsidered to define an active-region plane and the first contact 404 isconsidered to define a first-contact plane, the alternative interfacelocations 814 are shown between the active-region plane and thefirst-contact plane. Locating interfaces between the transparentportions 810 and the reflective portions 812 generally proximate to theactive-region plane or generally between the active-region plane and thefirst-contact plane can enhance lumen output and/or efficiency of theSSRT device 800. Emissions from the active region 416 directed towardthe first side 412 of the SSRT device 800 can pass through thetransparent portion 810 with little or no interference. Emissions fromthe active region 416 directed away from the first side 412 of the SSRTdevice 800 and toward the reflective portions 812 can reflect off theangled sides of the reflective portions 812 and be at least partiallyredirected toward the first side 412 of the SSRT device 800. In thisway, total internal reflection within the SSRT device 800 can be reducedand lumen output and/or efficiency can be increased.

FIGS. 9A-9B illustrate a method for making the SSRT device 800 shown inFIG. 8 according to an embodiment of the present technology. Onlyselected stages are shown to illustrate certain aspects of the presenttechnology. Initial stages in the process can be similar, for example,to those described above with reference to FIGS. 6A-6C. At the stageshown in FIG. 9A, the transparent layer 804 has already been formed overthe dielectric 406 and within the vias 602. The transparent layer 804can include, for example, indium tin oxide, doped zinc oxide (e.g.,aluminum- doped, gallium-doped, and indium-doped zinc oxide), aconductive polymer (e.g., polyaniline andpoly(3,4-ethylenedioxythiophene)), a carbon allotrope (e.g., carbonnanotubes and graphene), a combination thereof, or another suitablematerial. The transparent layer 804 can be formed using chemical vapordeposition, physical vapor deposition, atomic layer deposition, spincoating, patterning, combinations thereof, or other suitable formationprocesses known in the semiconductor fabrication arts.

FIG. 9B illustrates a stage in the process after the base portion 806has been formed on the transparent layer 804. The base portion 806 canbe formed using chemical vapor deposition, physical vapor deposition,atomic layer deposition, spin coating, patterning, combinations thereof,or other suitable formation processes known in the semiconductorfabrication arts. The side of the base portion 806 at the second side414 of the SSRT device 800 is shown generally flat, which can be theresult of a planarization process after forming the base portion 806.The base portion 806 can include a reflective contact material, e.g.,titanium, nickel, silver, aluminum, gold, or a combination thereof,among others. Similar to the base portion 428 of the SSRT device 400shown in FIG. 4, the base portion 806 is shown not directly contactingthe second semiconductor material 424. Accordingly, the composition ofthe base portion 806 can be selected according to factors other than itsability to form an adequate electrical connection with the secondsemiconductor material 424. For example, the base portion 428 caninclude silver when the second semiconductor material 424 includesN-type gallium nitride. In some embodiments, the reflective portions 812of the buried-contact elements 808 are formed separately from otherparts of the base portion 806. For example, parts of the base portion806 that the first contact 404 will block from receiving emissions canbe made in a separate step from a less reflective material than thereflective portions 812. Similarly, the base portion 806 canalternatively include two or more layers, e.g., a highly-reflectivelayer (not shown) adjacent to the transparent layer 804 and aless-reflective layer (not shown) spaced apart from the transparentlayer 804. The highly-reflective layer, for example, can include silver.After the stage shown in FIG. 9B, further processing can be performed,e.g., processing similar to that described above with reference to FIG.6F. This processing can include removing the growth substrate 600 andattaching the carrier substrate 410 (FIG. 8) to form the SSRT device 800shown in FIG. 8.

FIG. 10 is a partially-schematic, cross-sectional diagram illustratingan SSRT device 1000 configured in accordance with an embodiment of thepresent technology and having a second contact 1002 includingburied-contact elements 1004 with transparent portions 1006. In contrastto the SSRT device 800 shown in FIG. 8, the transparent portions 1006are not within a continuous transparent layer. A process for making theSSRT device 1000 can include planarizing the SSRT device 800 shown inFIG. 9A to remove portions of the transparent layer 804 (FIG. 9A)outside the vias (FIG. 9A) and then forming the base portion 806. Insome embodiments, the reflective portions 812 can have a differentcomposition than other parts of the base portion 806 and forming theSSRT device 1000 can include forming the reflective portions 812 on theSSRT device 800 shown in FIG. 9A and then planarizing reflectivematerial and transparent material to expose the dielectric 406. A planarpart of the base portion 806 can then be formed in a separate step. Theplanar part can have a composition that is less reflective than thecomposition of the reflective portions 812.

Any of the packaged SSRT devices described above with reference to FIGS.4-10 can be incorporated into any of a myriad of larger and/or morecomplex systems, a representative example of which is the system 1100shown schematically in FIG. 11. The system 1100 can include an SSRTdevice 1102, a power source 1104, a driver 1106, a processor 1108,and/or other subsystems or components 1110. The system 1100 can performany of a wide variety of functions, such as backlighting, generalillumination, power generation, sensing, and/or other functions.Accordingly, the system 1100 can include, without limitation, hand-helddevices (e.g., cellular or mobile phones, tablets, digital readers, anddigital audio players), lasers, photovoltaic cells, remote controls,computers, and appliances (e.g., refrigerators). Components of thesystem 1100 can be housed in a single unit or distributed over multiple,interconnected units, e.g., through a communications network. Thecomponents of the system 1100 can also include local and/or remotememory storage devices, and any of a wide variety of suitablecomputer-readable media.

The foregoing description provides many specific details for a thoroughunderstanding of, and enabling description for, embodiments of thepresent technology. Well-known structures and systems as well as methodsoften associated with such structures and systems have not been shown ordescribed in detail to avoid unnecessarily obscuring the description ofthe various embodiments of the disclosure. In addition, those ofordinary skill in the relevant art will understand that additionalembodiments can be practiced without several of the details describedherein.

Throughout this disclosure, the singular terms “a,” “an,” and “the”include plural referents unless the context clearly indicates otherwise.Similarly, the word “or” is intended to include “and” unless the contextclearly indicates otherwise. Directional terms, such as “upper,”“lower,” “front,” “back,” “vertical,” and “horizontal,” may be usedherein to express and clarify the relationship between various elements.It should be understood that such terms do not denote absoluteorientation. Reference herein to “one embodiment,” “an embodiment,” orsimilar formulations, means that a particular feature, structure,operation, or characteristic described in connection with the embodimentis included in at least one embodiment of the present technology. Thus,the appearances of such phrases or formulations herein are notnecessarily all referring to the same embodiment. Furthermore, variousparticular features, structures, operations, or characteristics may becombined in any suitable manner in one or more embodiments.

From the foregoing, it will be appreciated that specific embodiments ofthe technology have been described herein for purposes of illustration,but that various modifications may be made without deviating from thedisclosure. For example, each of the SSRT devices 400, 500, 700, 800,1000 shown in FIGS. 4-10 includes two interconnected buried-contactelements. It will be understood by a person of ordinary skill in therelevant art that the illustrated buried-contact elements arerepresentative only and that SSRT devices configured in accordance withthe present technology can include any suitable number of buried-contactelements. For example, additional buried-contact elements can be presentto the left and/or to the right of the buried-contact elements shown inFIGS. 4-10 and the illustrated buried-contact elements can be from asingle row of a much larger array of buried-contact elements. Certainaspects of the technology described in the context of particularembodiments may be combined or eliminated in other embodiments. Forexample, the color-converting component 502 and the encapsulant lens 504of the SSRT device 500 shown in FIG. 5 can be combined with the SSRTdevices 700, 800, 1000 shown in FIGS. 7, 8, and 10. Additionally, whileadvantages associated with certain embodiments of the present technologyhave been described in the context of those embodiments, otherembodiments may also exhibit such advantages, and not all embodimentsneed necessarily exhibit such advantages to fall within the scope of thetechnology. Accordingly, the disclosure and associated technology canencompass other embodiments not expressly shown or described herein.

I claim:
 1. A solid-state radiation transducer device, comprising: a radiation transducer including a first semiconductor material, a second semiconductor material, and an active region between the first semiconductor material and the second semiconductor material; a first contact electrically coupled to the first semiconductor material; a plurality of vias extending through the first contact, the first semiconductor material, and the active region; and a second contact electrically coupled to the second semiconductor material, the second contact including a plurality of buried-contact elements within the vias, wherein the buried-contact elements are at least partially transparent.
 2. The solid-state radiation transducer device of claim 1, wherein the radiation transducer is a light-emitting diode.
 3. The solid-state radiation transducer device of claim 1, further comprising a transparent dielectric in the vias between the buried-contact elements and the first contact, the first semiconductor material, and the active region.
 4. The solid-state radiation transducer device of claim 1, wherein the buried-contact elements include indium tin oxide, zinc oxide, or a combination thereof.
 5. The solid-state radiation transducer device of claim 1, wherein individual buried-contact elements include a transparent portion, and the second contact further includes one or more reflective portions adjacent to the transparent portions at least at the vias.
 6. A light-emitting diode device, comprising: a light-emitting diode including a first semiconductor material, a second semiconductor material, and a light-emitting region between the first semiconductor material and the second semiconductor material; a first contact electrically coupled to the first semiconductor material; a plurality of vias extending through the first contact, the first semiconductor material, and the light-emitting region; and a second contact electrically coupled to the second semiconductor material, the second contact including a plurality of buried-contact elements within the vias, wherein individual buried-contact elements have a transparent portion adjacent to the second semiconductor material.
 7. The light-emitting diode device of claim 6, wherein the second contact further includes one or more reflective portions adjacent to the transparent portions at least at the vias.
 8. A solid-state radiation transducer device having a first side and a second side facing away from the first side, comprising: a radiation transducer including a first semiconductor material, a second semiconductor material, and an active region between the first semiconductor material and the second semiconductor material; a first contact electrically coupled to the first semiconductor material and positioned generally between the first semiconductor material and the second side; and a second contact electrically coupled to the second semiconductor material and positioned generally between the second semiconductor material and the second side, wherein the second contact includes a plurality of buried-contact elements with individual buried-contact elements having a transparent portion adjacent to the second semiconductor material.
 9. The solid-state radiation transducer device of claim 8, wherein the radiation transducer is a light-emitting diode.
 10. The solid-state radiation transducer device of claim 8, wherein the first contact defines a plane, and the buried-contact elements have generally straight sidewalls from the plane to the second semiconductor material.
 11. The solid-state radiation transducer device of claim 8, wherein the second contact includes a generally continuous, conductive, transparent layer including the transparent portions.
 12. The solid-state radiation transducer device of claim 8, wherein: the second contact includes a base portion extending between the buried-contact elements, the base portion is reflective at least at the buried-contact elements, the buried-contact elements extend between the base portion and the second semiconductor material, and the buried-contact elements are transparent.
 13. The solid-state radiation transducer device of claim 8, wherein the transparent portions include indium tin oxide, zinc oxide, or a combination thereof
 14. The solid-state radiation transducer device of claim 8, wherein the transparent portions include a transparent alloy including a conductive, transparent material and the second semiconductor material.
 15. The solid-state radiation transducer device of claim 8, wherein individual buried-contact elements include a reflective portion, and wherein the transparent portions are between the reflective portions and the second semiconductor material.
 16. The solid-state radiation transducer device of claim 15, wherein the reflective portions are generally tapered inwardly in a direction toward the second semiconductor material.
 17. The solid-state radiation transducer device of claim 15, wherein the second semiconductor material includes N-type gallium nitride and the reflective portions include silver.
 18. The solid-state radiation transducer device of claim 15, wherein: individual buried-contact elements include an interface between the reflective portion and the transparent portion, the active region is at least partially planar and defines an active-region plane, the first contact is at least partially planar and defines a first-contact plane, and the interfaces are generally proximate to the active-region plane or generally between the active-region plane and the first-contact plane.
 19. The solid-state radiation transducer device of claim 18, wherein the reflective portions are generally tapered inwardly in a direction toward the second semiconductor material.
 20. A light-emitting diode device, comprising: a light-emitting diode including a first semiconductor material, a second semiconductor material, and an active region between the first semiconductor material and the second semiconductor material; a first contact electrically coupled to the first semiconductor material; a second contact including a plurality of buried-contact elements electrically coupled to the second semiconductor material; and an optical component including a transparent matrix and color-converting particles within the matrix, wherein the color-converting particles are configured to absorb radiation from the light-emitting diode at a first wavelength range and emit radiation at a second wavelength range different from the first wavelength range, radiation emitted by the color-converting particles includes backscatter radiation, and the light-emitting diode device has an average reflectivity of backscatter radiation from the color-converting particles at the buried-contact elements greater than about 75%.
 21. The light-emitting diode device of claim 20, wherein the light-emitting diode device has an average reflectivity of backscatter radiation from the color-converting particles at the buried-contact elements greater than about 80%.
 22. The light-emitting diode device of claim 20, wherein individual buried-contact elements have a transparent portion directly adjacent to the second semiconductor material.
 23. The light-emitting diode device of claim 20, wherein individual buried-contact elements include a transparent alloy including a conductive, transparent material and the second semiconductor material.
 24. The light-emitting diode device of claim 23, wherein the conductive, transparent material includes indium tin oxide, zinc oxide, or a combination thereof
 25. A method of making a solid-state radiation transducer device, comprising: forming a radiation transducer having an active region between a first semiconductor material and a second semiconductor material; forming a first contact electrically coupled to the first semiconductor material; forming a via extending through the first contact, the first semiconductor material, and the active region; and forming a transparent member within the via electrically coupled to the second semiconductor material.
 26. The method of claim 25, further comprising forming a transparent dielectric within the via, and removing a portion of the transparent dielectric within the via to expose the second semiconductor material before forming the transparent member.
 27. The method of claim 25, further comprising forming a reflective member electrically coupled to the transparent member.
 28. The method of claim 27, wherein forming the transparent member includes annealing a transparent material and the second semiconductor material to form a transparent alloy prior to forming the reflective member.
 29. The method of claim 27, wherein forming the transparent member includes forming a transparent layer and planarizing the transparent layer prior to forming the reflective member.
 30. The method of claim 27, wherein forming the reflective member includes forming an interface between the reflective member and the transparent member, the interface being generally proximate to a plane defined by the active region or generally between the plane defined by the active region and a plane defined by the first contact.
 31. The method of claim 27, wherein forming the reflective member includes forming the reflective member generally tapered inwardly in a direction toward the second semiconductor material.
 32. The method of claim 27, wherein forming the first contact includes forming the first contact with N-type gallium nitride and forming the reflective member includes forming the reflective member with silver. 